1. Field of the Invention
The present invention relates to a method for driving a liquid crystal display assembly.
2. Description of the Related Art
With a liquid crystal display device, a liquid crystal material itself does not emit light. Accordingly, for example, a direct planar light source device (backlight) for illuminating a display area of a liquid crystal display is disposed at the back of the display area. Note that with a color liquid crystal display, one pixel is made up of three sub pixels of a red light emitting sub pixel, a green light emitting sub pixel, and a blue light emitting sub pixel. Liquid crystal cells making up each pixel or each sub pixel are operated as a sort of light shutter (light valve), i.e., the optical transmittance of each pixel or each sub pixel is controlled, thereby controlling the optical transmittance of illumination light (e.g., white light) emitted from a planar light source device, and displaying an image.
An existing planar light source device in a liquid crystal display assembly illuminates the entire display area with even and constant brightness. This state is schematically illustrated in (A) in FIG. 12 and (A) in FIG. 13 as the luminance of the planar light source device (sometimes referred to as light source luminance). Controlling the optical transmittance of pixels A and B (see (B) in FIG. 12 and (B) in FIG. 13) enables the luminance (sometimes referred to as display luminance) of a part of a display area corresponding to the pixels A and B to be controlled (see (C) in FIG. 12 and (C) in FIG. 13). Now, let us say that the pixel A is located at the upper portion of the liquid crystal display, and the pixel B is located at the lower portion of the liquid crystal display.
Note that later-described (A) in FIG. 14(A) and (A) in FIG. 15(A) are diagrams schematically illustrating light source luminance, (B) and (C) in FIG. 14 schematically illustrate the optical transmittance and display luminance of the pixel A, and (B) and (C) in FIG. 15 schematically illustrate the optical transmittance and display luminance of the pixel B. The horizontal axes of FIG. 12 through FIG. 15 illustrate the time course (number of frames) of image display.
Also, a planar light source device having another configuration different from such a planar light source device, i.e., a planar light source device, which are configured of multiple planar light source units, for changing a distribution of illuminance at multiple display area units making up a color liquid crystal display has been known from Japanese Unexamined Patent Application Publication No. 2005-17324. Note that such a planar light source device made up of multiple planar light source units are sometimes referred to as a time-sharing-driven planar light source device for the sake of convenience.
Further, controlling a planar light source device based on a later-described method has been disclosed in Japanese Unexamined Patent Application Publication No. 11-109317, for example. Specifically, let us say that the maximum luminance in the planar light source device is taken as Ymax, and the maximum value (specifically, 100% for example) of the optical transmittance (aperture ratio) of a pixel at a display area is taken as Ltmax. Also, let us say that when the planar light source device has the maximum luminance Ymax, the optical transmittance (aperture ratio) of the pixel for obtaining display luminance y0 in the display area is taken as Lt0. In this case, the light source luminance Y0 of the planar light source device needs to be controlled so as to satisfyY0·Ltmax=Ymax·Lt0 
Note that a conceptual diagram regarding such control is illustrated in (A) and (B) in FIG. 16. Here, the light source luminance Y0 is changed for each frame.
Specifically, for example, in the event that the light source luminance (Y0) is controlled such as schematically illustrated in (A) in FIG. 14 and (A) in FIG. 15, and additionally, the optical transmittance Lt of a pixel is controlled such as schematically illustrated with the solid lines in (B) in FIG. 14 and (B) in FIG. 15, the display luminance (y) at the pixels A and B such as schematically illustrated with the solid lines in (C) in FIG. 14 and (C) in FIG. 15 can be obtained.